Process of burning lime.



A. E. TRUESDELL. PROCESS oF BURNING LlrvIE. APPLICATION FILED IULY3I, ISIZ.

Patented Apr. 25, 1916.

ARTHUR E. TRUESlEElLL, 01E .dlDhlhSg SSACHUSETTS.-

rnocnss or nonnina miur.

insures.,

Specification of Letters Patent.

Application filed July 3l, 191%. Serial No. titten.

tion with the accompanying drawing, is va specincation, like characters on the drawing reyroresenting like parts.

rlhis invention relates to a new and use- 'ful process of burning lime by which limev stone, and especially limestone of a soft nan ture, can be more economically burned in a rotary kilnthan is possible with any of the processes now in use, and further to provide a novel process by which the lime will be more uniformly burned and a higher grade product will be. produced than is possible with the rotary kiln processes which ,havel heretofore been used..

in burning lime in the rotary kiln the usual process is, hrst, to crushthe limestone to such a size las to pass a ring four inches in diameter or less (depending somewhat on the nature ofthe stone) and then to introduce the -crushedlimestone without screening into the rotary kiln? This crushed mate rial contains particles or lumps which vary greatly in sire, and sometimes it contains as high as ten per cent. of limestone dust or powder. ls the heat economy of a rotary kiln is naturally low, attempts have been. made to increase their emciency by introduc boilers and economizers into the path of the waste gases and by using dust chambers to prevent as much as possible the clog ging of the draft passages through the boil ers. lt was found, however, that the waste` heat boilers and dust' chambers entailed considerable expense in cleaning and keeping.

in order besides interfering more or less with the continuous operation of the kiln, and to avoid this difficulty it has been proposed to utilize the waste heat from tle rotary kiln to burn the limestone partially in a vertical kiln instead of utilising it in boilers, economizers, etc., and then to feed. the partially-burned limestone from the vertical kiln into the rotary kiln where the burning 'operation was completed. Where the vertical kiln was thus used it was found to be necessary to keep thelimestone in as large pieces as practicable and with a minimum dust content in order to prevent the draft/through the re ,al `kiln from hecomu ing unduly clogged, and inv order to secure a proper and complete burning of the large lumps or pieces before their discharge from the rotary kiln it was found necessary to maintain the temperature `in the vertical kiln substantially at the point of disassocia tion from the limestone of its CU2 gas, for if a lower temperature were employed in the vertical kilnthe amount which the large lumps were burned in the rotary kiln was `not sufcient to enable them to be completely burned during their passage through the rotary kiln, ln such case an incornpletely burned product would result.

The disadvantages which developed the practical operatiouof the above processes were that where the large lumps were introduced into the vertical kiln the product was apt to be unevenly burned since both large lumps and small particles were subu jected to the same heating; the use of wastey heat boilers and y dust' chambers involved considerable expense in keeping them-clean 'and caused more or less variation in the draft and also interfered with the continu ous operation of the kiln; and the practical use of a vertical kiln with a. rotary kiln as above outlined involved the use of an en haust fan of large capacity and consequent heavy charge for power in order to maintain a proper draft.

l have improved the processes of burning lime above referred to in such a way as to produce a uniformly-burnt lime in a h ne state with a minimum expenditure of fuel,

'and ll accomplish this by hrst pre-heating uncrushed limestone to a temperature Suthcient to soften it so that it will readily' disintegrated, but insuflicient to edect the :.1

disassociation therefrom of its CZ gas, and then passing the heated limestone through a disintegrator which readily disintegrates or granulates and reduces it to a uniform granular condition, and then parsn ing the disintegrated limestone through a rotary kiln where it is properly burned. "llhe pre-heating of the rock to the desired temperature is 'accomplished entirely by heat which is discharged from the rotary kiln and, therefore, without the espenditure of any fuel other than that which is re quired for burning the lime, and the operation of crushing or disintegrat'ing the limeratentea apr, es, rara lou stone after it has thus been heated can be it accomplished will will umh less espenditure of power than whenjthe limestone cold. \By my process, therefore,"I not only Aproduce a high grade lime of uniform size, but I secure it by aminimum expenditure of ower-and fuel and thus on an economical asls.

Referringto ,the drawings wherein I havel to burn the lime in a' rotary kiln. The lime struction but is desirable.

is discharged from the rotary kilnv into a rotary cooler 4, as usual.) The construction and operation of the rotary kiln and its associated gas producer is well known to those skilled in the art and need not be further described. The stationary and rotary kilns are so situated relative to each other that the hot gases which are discharged from the rotary kiln pass into the lower end ofthe stationary kiln 1 and are discharged throu the stack 5 thereof. Situated between't e rotary kiln and the stationary kiln is a disintegrator 6 whichmay be of any suitable conpreferably a rotary disin- K tegrator through which the limestone passes in moving from the stationary to the rotary kiln. This disintegrator l is sustained in suitable bearings 7 and is rotated by any suitable means,

As herein shown it is provided with exteriorvgear teeth 8 which mesh with and are driven byva suitable driving gear. The ldisintegrator will preferably be provided on its interior with vprojections `or other means which will operate to disin- 40 tegrate the material passing therethrough.

The disintegrator is arranged to receive limestone from the' lower end -10 ofv the stationarypklln and to discharge it into the upper end of the rotary kiln.

In` carrying.- out my invention the limestone in its natural state and without being crushed is delivered into the stationary kiln 1 through the opening 20 and it is fed'from the lower end' of the stationary kiln to the i disintegrator by` any suitable means, such as the reciprocating plunger 11'. During the burning operation-the heat from the rotary kiln passes up through the stationary kiln 1 and heats the limestone 12 therein to a point at' which it is easily disintegrated.- The limestone, coarse and ne,is then passed into the disintegrator 6 in which it becomesthoroughly disintegrated and reduced to granular form of practically uniform size, this operation being very `easily accomplished and at such speed as may be with A.the expenditure of a minimum amount of power because of the fact that the limestone is in an easily-disintegrable condition.

' IThe disintegrated limestone is then deliv- Having fully described my invention, what I I claim as new and desire ters Patent is 1. The process of burning lime which consists first in passing uncrushed limestone in lump formation through a vertical kiln and heating it therein to a temperature where it will readily disintegrate,.but which is insufficient to efect the disassociation therefrom of its CO2 gas, then passingthe heated limestone through a disintegrator in which the lumps are disintegrated and reduced to a granular form, and thence passing it into a rotary kiln where -it is burned.

2. The process of burning lime which consists in passing uncrushed limestone in lump formation through a vertical kiln which is arranged to receive the hotgases delivered from a rota-ry kiln, utilizing said hot gases to heat the limestone in the vertical kiln to a temperature where it will readily disintegrateA but `which is insufiicient to effect the disassociation therefrom of its CO2 gas, passing the heated limestone through a disintegratorv in which the lumps are disintegrated and vreduced .to al granular form, and then passing it into said rotary kiln Where it is reduced to an oxid state.

3. The process of burning lime which consists .in first heating uncrushed limestone as it comes from the quarry to a temperature at to secure by Let- 4which it will readily disintegrate, but which is insuiicient to effect the disassociation therefrom of its CO2 gas, disintegrating the heated limestone whilel it is still being subjected to the heat/ing operation thereby to reduce the limestone to substantiallyuniform granular form `and then subjecting the dis- ARTHUR E. TRUESDELL. Witnesses:

B. H. KENNEDY, E. TRUESDELL.

higher tempera- ...mammina- 

